The present disclosure relates generally to LED light bulbs, and more specifically to LED light bulbs capable of replacing conventional light bulbs.
As well known in the art, there are different kinds of lighting fixtures developed in addition to the familiar incandescent light bulb, such as halogen lights, florescent lights and LED (light emitting diode) lights. LED light bulbs have several advantages. For example, LEDs have been developed to have lifespan up to 50,000 hours, about 50 times long as a 60-watt incandescent bulb. This long lifespan makes LED light bulbs suitable in places where changing bulbs is difficult or expensive (e.g., inaccessible places like the exterior of buildings). Furthermore, an LED requires minute amount of electricity to reach a luminous efficacy about 10 times higher than an incandescent bulb and 2 times higher than a florescent light. As power consumption and conversion efficiency are big concerns in the art, LED light bulbs are expected to replace several kinds of lighting fixtures in the long run.
Unlike incandescent light bulbs and florescent lights whose lights are omnidirectional, an LED transmits a focused beam of light. Defined by ENERGY STAR, a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy, any lighting fixture proclaiming to replace an existing standard omnidirectional lamp or bulb is required to meet specific luminous intensity distribution. FIG. 1 demonstrates a lighting fixture intended to replace omnidirectional lamps or bulbs. There are some requirements for lighting fixtures intended to replace omnidirectional lamps or bulbs. As shown in FIG. 1, the distribution of luminous intensity shall be even within zone Zfront, the 0° to 135° zone, (vertically axially symmetrical) and the luminous intensity at any angle within zone Zfront shall not differ from the mean luminous intensity for the entire zone Zfront by more than 20%. Furthermore, at least 5% of total flux must be emitted in zone Zrear, the 135° to 180° zone, in the proximity of the base contact. Light reflectors, diffusers, and lens have been employed in LED light bulbs, to spread out the focused light beam of an LED. Nevertheless, it is still a challenge for an LED light bulb to meet the intensity distribution requirements of ENERGY STAR.